Well, that would depend on who you are asking. If you were to ask a Roman Catholic this question, you would get an answer that would discuss the apparent lack of unity between the different juristictions within Orthodoxy.Compared to the apparent unity, created by the pope, in the Roman Catholic Church. Rome has also accused the Orthodox as being to mystical, in its theology.But if you were to ask an Orthodox this question, like myself, he/or she, might say somthing like this: I think that the real difference lies whithin the whole way in wich the Orthodox aproach and think about God and man, expecially concerning salvation. We see salvation as a much more ontological issue, while Rome sees salvation in a much more judicial way. In other words, we Orthodox, see salvation as having to deal much more with who we were in paradise, what we became after the fall, and who we can and will become by the Grace of God transforming us through Jesus Christ. The Roman Catholic Church adopted a view of salvation that was much different than that of the first thousand years when that two Churches were one. They see man(since the fall) as being born in a state of Guilt, and that Christ had to pay for and suffer for our guilt before God the father, Jesus had to make satisfaction or satisfy an angry and just God, with an eternil sacrifice that would eternally satisfy God's justice and wrath. Therefore, Rome also sees the suffering Christ as central to their doctrines about salvation. The Orthodox way of seeing things is much different. We believe that Christ, through His suffering and death of the Cross, Triumphed over death and suffering. He destroyed death by death, as we say. And then he raised us up(human nature) and acended into heaven. Through our union with Christ, we ,too, can now share and participate in the Life of God, and be transformed by the Grace of God and become like Christ. So the Resurection, in the mind of the Orthodox, takes a more prominent role in our whole way of thinking about salvation. As St. Paul says, "If Christ is not risen, then our faith is in vain". So Christ's suffering alone, is not the focus of the Gospel. It is his resurection, his victory over death, for our sakes, that we Orthodox center our thinking on. What did Christ acomplish through his Incarnation, His life, His suffering and death of the Cross do for us? This is the area were you will find the biggest difference between Orthodox theology and Roman Catholic. I hope this helps you a little. There is a great book by Bishop Kallistos Ware called The Orthodox Church, that speaks about all of this, in a much better way than I ever could. I highly recomend it. God bless you in your search.